DICYANAMIDE COMPLEXES OF COPPER(II), NICKEL(II) AND COBALT(II) WITH BENZIMIDAZOLE AND ITS 2-ALKYL-DERIVATIVES

Dicyanamide complexes of Cu-II, Ni-II and Co-II of the type M[N(CN)(2)](2)L(2), where L=benzimidazole, 2-methyl- or 2-ethylbenzimidazole, have been prepared and studied by spectroscopy and magnetochemistry. The complexes, except for Co[N(CN)(2)](2) (benzimidazole)(2), are six-coordinate, involving bidentate bridging dicyanamide groups. While the Ni-II complexes have practically octahedral structures, the Cu-II complexes are pseudooctahedral with similar tetragonal distortion. The ligand field strength in these complexes depends mainly on the steric effect of the benzimidazole ligands. The Co-II complex of benzimidazole is monomeric tetrahedral, but that of 2-ethylbenzimidazole is tetragonal octahedral. The oridging function of dicyanamide in the six-coordinate complexes is realized either through both cyanide or through amide and cyanide nitrogens. The complex Cu[N(CN)(2)](2) (2-methylbenzimidazole)(2) is a weak antiferromagnet (J=-O.1cm(-1)), exhibiting under ca. 15 K a long-range antiferromagnetic ordering.